Electric motor systems are known in which windings on a stator are powered by a DC to AC converter, such that the windings generate magnetic fields that cause a rotor to rotate. The windings are electrically insulated by insulators. However, electrical charges build-up on the surfaces of insulating material during use, causing a high electric field to build up and an electrical breakdown to subsequently occur. Such an electrical breakdowns generate a relatively large amount of heat, which degrades the insulation material.
It is possible to use high performance insulating materials and configurations to prevent or reduce this problem. However, such techniques increase the size, cost and/or complexity of manufacturing the motor system.